Precise Local Gain Extraction in a Phase-Modulated Correlation-Domain Brillouin Fiber Sensor

Background gain arising from pump-probe energy transfer at off-peak positions considerably limits the performance of a phase-modulated Brillouin optical correlation domain analysis (BOCDA) fiber sensor. Here, we deeply analyze the properties of the background gain. Then, based on its generation mechanism, a simple subtraction algorithm is proposed to remove background gain from measured raw correlated gain, resulting in precise local gain extraction. There is no need to modify the current fully-optimized BOCDA setup or increase the data acquisition time. In a proof-of-concept experiment with a sensing distance of 1032.3 m and a spatial resolution of 3.5 cm, the BFS estimation error is reduced from 1.3 MHz to 0.2 MHz owing to our method.